1. Field of the Invention
The present invention relates to the field of digital signal processing, and more specifically, to systems and methods for estimating the offset between the actual sample-clock-frequency used by a receiver's analog-to-digital converter and an intended sample-clock-frequency.
2. Description of the Related Art
At a transmitter, a stream of information bits is mapped into a stream of complex symbols {Un} in a constellation (i.e., a set of points in the complex plane), e.g., a QAM constellation. The stream of symbols {Un} may be supplied to a subsystem that converts the symbol stream into an analog baseband signal u(t). The analog baseband signal u(t) may be used to modulate a carrier signal. The modulated carrier is transmitted through a channel, e.g., a wired channel such as a cable, a wireless channel such as the atmosphere or free space, a fiber optic channel, etc. A receiver captures a channel-distorted version of the transmitted signal from the channel, recovers a baseband signal from the captured signal, and samples the baseband signal. However, the sampling clock rate 1/TS′ used by the receiver is in general different from an intended sampling clock rate 1/TS. This offset between the intended clock rate 1/TS and the actual clock rate 1/TS′ makes it difficult to accurately demodulate the received baseband signal. Thus, there exists a need for methods, especially low-complexity methods, for estimating this clock rate offset.